This invention relates generally to lighting fixtures and, more particularly, to lighting fixtures adapted to image a high-intensity beam of light at a distant location.
Lighting fixtures of this particular kind are commonly used in theater, television and architectural lighting applications. Many such fixtures include an ellipsoidal or near-ellipsoidal reflector with a single lamp located generally coincident with the reflector's longitudinal axis. The reflector has two general focal regions, and the lamp is positioned generally with its filaments located at or near one of those focal regions such that light emitted from the filaments is reflected by the reflector generally toward the second focal region. A gate aperture is located at that second focal region, and shutters, patterns and the like can be used at that gate for shaping the projected beam of light. A lens located beyond the gate images light passing through the gate aperture at a distant location.
One problem commonly encountered by lighting fixtures of this kind is that an excessive amount of light emitted by the lamp is not incorporated into the projected beam, but instead is misdirected and absorbed by the shutters, patterns, gate and other internal components of the fixture. This wastes electrical energy and leads to undesired heating of the fixture. In many instances, the shutters and patterns can be warped by the excessive heat and therefore need to be frequently replaced.
Another problem encountered in lighting fixtures of this kind is that the imaged light beam can sometimes have an intensity that varies radially such that a concentric ring pattern is provided. This undesired concentric ring pattern occurs because of the particular kind of filament used in the lamp, e.g., a coiled coil. Each point on the reflector reflects light toward the gate so as to produce a magnified image of the filament, and the superposition of the images resulting from all points on the reflector sometimes can provide the concentric ring pattern.
This undesired concentric ring pattern has been overcome by providing the reflector with a plurality of small, trapezoidal facets, typically flat sections, that function to blur the projected image. The facets have edges that are arranged both radially and circumferentially. Although such a reflector structure is generally effective in eliminating the concentric ring effect, it is believed that this solution misdirects an excessive amount of light so as not to be incorporated into the projected beam.
Another drawback to lighting fixtures of the kind described above is that the fixture projects an undesired amount of infrared light along with the desired visible light. This unduly heats the area on which the projected light is imaged, which in the case of theater, television and some architectural lighting can lead to substantial discomfort. Reflecting undesired infrared light also leads to undesired heating of the pattern and shutters located at the gate and of any colored media or gels located forwardly of the lens. In some cases, highly absorptive media, such as blue gels, burn out very quickly or cannot be used at all.
It should therefore be appreciated that there is a need for an improved lighting fixture that images a beam of light at a distant location, yet that is not unduly wasteful of energy and that does not unduly transmit undesired infrared light. The present invention fulfills this need.